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Water - Safe to Drink? Nepal
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Water source, Meatu District, Tanzania
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Mwamongu Village water source, Tanzania
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Water source in Dar es Salaam, Tanzania
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The presence of the bacterium Escherichia coli indicates recent fecal contamination of water.
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Components of the Portable Microbiology Laboratory
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Portable Microbiology Laboratory. Materials for 25 water tests in gallon-sized plastic bag
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Bob Metcalf holds the two Portable Microbiology Laboratory tests: Colilert MPN tube, and E. coli count Petrifilm.
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Colilert: A presence/absence test for E. coli in 10 ml of water.
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ONPG and MUG are the two substates for E. coli in Colilert
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How to use Colilert MPN. Collect water in sterile WhirlPak (open well in Temeke Municipality, Dar es Salaam, Tanzania)
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Carefully remove cap from Colilert tube
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Use sterile pipette to add 10 ml of water source
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Carefully replace cap
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Shake tube to dissolve chemicals
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Incubate at body temperature to allow 20-24 doublings of bacteria, usually 10-18 hours
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Results appear in 12-24 hours. Clear = no coliform bacteria. Yellow (ONPG+) = coliform bacteria present
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Use a battery-operated long UV light to shine on tubes. Blue fluorescence = MUG +, E. coli is present, water not safe to drink.
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The best test for E. coli in foods: E. coli Count Petrifilm
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Two substrates in Petrifilm for E. coli, lactose and BCIG
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To use Petrifilm, label sample source and time
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